Apparatus for precasting concrete stair structures



F. KIOGL July 18, 1944.

APPARATUS FOR PRECASTiNG CONCRETE STAIR STRUCTURES 4 sheets-sheet 1 4 Filed May 28, 1941 Fawn Kom.

F. KOGL Filed May 28, 1941 4 Sheets-Sheet 2 APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES July 18, 1944.

July 18,1944. F. Kosl f 2,353,676

APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES Filed May 28, 1941 4 sheets sheet 3 I Fawn Rom.

(L ban/1 I F. KOGL July 18, 1944.

APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES Filed May 28, 1941 4 Sheets-Sheet 4 nN v Q 4 \N MM Penna. KOGL 3% M I W4 Patented July 18, 1944 APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES Frank Kogl, St. Paul, Minn., assignor offour per cent to Minnie M. Clark, South St. Paul, Minn., two and one-half per cent to Walter H. Carlson, two and one-half per cent to Ora E. Carlson, ten per cent to Ruby S. McBride, and four per cent to Genevieve Clark, all of St. Paul,

Application May 28, 1941, Serial No. 395,558

15 Claims.

This invention relates to a mold or apparatus for precasting concrete stair structures.

The primary object of the invention is to provide a mold for casting any desired number of steps in one monolithic unit, and with a surmounting platform extension if desired, thus making the structure particularly useful as outdoor steps or stoops for buildings. A further object is to provide a mold which may be conveniently adjusted to cast the desired number of steps, with or without platform extension, and which once adjusted, may be used repeatedly to rapidly and effectively cast the units. Still another object is to provide a mold arranged to cast a nosing around the edges of the step treads and platform.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in Which- Fig. 1 is a side elevation of the mold complete for casting four steps and a platform in one monolithic unit.

Fig. 2 is a rear view, on a reduced scale, showing a stair structure as cast in my mold, looking at the same from the platform end.

Fig. 3 is an enlarged fragmentary section through adjacent portions of outer tread and riser forming portions of the mold showing the detachable connection therebetween.

Fig. 4 is a fragmentary sectional view through an upper end of the mold in its inverted, casting position showing a cut-off or bafile device for reducing the height of the cast structure.

Fig. 5 is a longitudinal vertical section through the mold, showing it in inverted casting position and supported in its stand.

Fig. 6 is an enlarged vertical cross section along the line 65 in Fig. 1 but showing only a side portion of the mold.

Fig. 7 is an enlarged plan view of a rear corner portion of the mold in its inverted or casting position.

Fig. 8 is a fragmentary vertical cross section along the line 88 in Fig. 7.

Fig. 9 is a fragmentary horizontal cross section along the line 99 in Fig. 1.

Fig. 10 is a plan view of the mold in its inverted casting position showing only the platform and uppermost step casting portions of the mold.

This application is a continuation in part from m copending application Serial No. 278,711, filed June 12, 1939, for a Method for preoasting concrete stair structures. The present application further embodies methods and constructional details found in my prior United States Patent No; 2,161,822, issued June 13, 1939, and my copending applications Serial No. 287,513, filed July'31,'1939, for an Apparatus for precasting concrete stair structures and Serial No. 388,772, filedApril 16, 1941, for Concrete stair structure.

Referring now with more particularity and by reference characters to the drawings, the mold or apparatus constituting my invention is indicated generally at A and is seento conipriseasits basic elements an outer. form B and inner form C. These forms are assembled, in the set up condition of the mold shown in Figs 1 and 5, to provide intervening cavities and recesses which, when filled with the cementitious mixture, will form and cast a step structure of the type shown in Fig. 2. This structure comprises a se ries of four steps each having a tread T, and a riser R, a surmounting flat platform P,}and the panelled sides or side walls S, all of monolithic construction, as shown. The wall thickness'at all points may be of any desired dimensionbutit is of course understood that the entire underside of the structureis hollow in order tqgreduce weight and quantity of material required.

nosing N surrounds the ends and outer'exposed edge of each tread T as clearly shown.

Turning nowto the construction'of the mold itself, the outer form B thereof comprises a plu rality of side sections or side plates which, in their assembled relation, are set and joined on edge vertically and define the outer surfaces .of the stair sides S. Each side section is of a width (vertically) corresponding to the height 'of the risers R and the sections accordingly are in number equal, at each side of the form, to the num ber of steps to be cast. In the .mold shown a maximum of four steps may be cast and theside sections are accordingly represented by the reference numerals In, ll, [2, and I3 in progressive order, it being understood, however, that the mold may be constructed to have a maximum step capacity either more or less than that here shown. I

These side sections l0 through 13 are formed of fiat metal sheets or plates of rectangular shape and grow progressively shortereach'successive step upward, tothereby terminate at a common vertical plane at their rear ends-I14. The margins are braced by angle irons designated generally at l5, spot welded or otherwise secured in place, and which also form means for attaching the sections to each other and to othercom' ponent parts of the mold. To this end, and as-a representative fastening means, I provide i the angle irons with registering apertures in their outwardly turned webs and through which are placed diametrically slotted pins I! for the reception of wedges or keys l8 which, when driven tight, holds the parts rigidly together. This type of fastener meets the requirement of a rigid and quickly manipulated means for assembling the sections, but I may of course employ bolts IT, spring latches, or other suitable means as may be desired.

In the mold assembly, therefore, four of the side sections are set up on edge and secured together at each side of the mold, and present a plane inner surface well adapted toform and define the outersides of the steps;

The forwardly projecting forward ends and upper edges of the side sections 1 ll through I3 form supports for the four riser and tread forming members or outer riser and tread forms '25:, 2|, 22,v and 23 which are removably secured transe versely across these edges of the assembled mold sides. Each of these forms through 23 is substantially identical in shape and size and comprises a vertical riser plate 24 and horizontal tread plate 25 forming a right angled structure as shown. The ends of .the forms are provided with notches 26 in both their vertical and horizontal portions for the reception of .clamp bolts 21 which are pivotedat their ends 28 to each side section 10 to l3 in position to swing at, their free ends into said notches. The vertical plates 24, braced by end bars 24 are then drawn tight against the forward angle irons 15 by wing nuts 28 screwed on the forwardly directed bolts 21 and the horizontal plates, 25. which are braced by similar end bars 2 are similarly drawn tight by the wing nuts 30 screwed upon the upwardly directed draw bolts as clearly shown iii-Fig. 1.

It. will be noted that the forwardly projecting upper edges ofv each side section 50 through is are provided with outwardly bulged and angled portions .3! and the conn ti f ont edge P tions of the plates .24 and 25 of each outer tread and riser form 20 through 23 are similarly formed '5 designated at 32, the said portions 3! being coped at 33 into the portions 32 to fit nicely thereinto. As .a result the ends and forward edges of the treads T of the finished stair structure will be provided with the desired nosing N as heretofore described.

The lower margins of the outer form members 2| through 23 are turned smoothly forward to provide a rounded junction line between adjacent treads and risers T and R and these margins carry transversely extending upwardly spaced and downwardly and forwardly tongued clips 35 adapted to fit the upwardly and rearwardly turned edges of strips 35 secured to the upper margins of the forms 20 through 22, as best seen in Fig. 3. These connections between the forms 20-23 provide rigid fastening means but permit them to be swung clear one at a time (upper one first) as seen in Fig. l and as will be more particularly pointed out hereinafter. The meeting edges of the forms butt smoothly together in a common plane to provide a smooth casting surface for'the treads T.

The inner form C is somewhat similarly constructed and comprisesas here shown the two sides each made up of four inner side sections 42, 43, 44, and which are formed of sheet material and have marginal angles 46 secured to meeting edges and on their inner surfaces. These riser form members which in this case comprise horizontally disposed and transversely extending tread plates 59 and similarly extended but verside sections are set up on edge and secured together by any suitable means such as bolts of the cast steps.

spective side sections 42 through 45 and have openings 53 which leave only surrounding marginal frame portions but which are adapted to be closed by removable cover plates 5d. Said plates 54 are flanged at their edges 55 for stiffening purposes and when laid over the openings overlie the margins thereof and rest between forks or clips 56 secured to the plates 50 and adapted to receive the removable retaining bolts 5?. These bolts engage at their heads 58 with the forward forks 56 and at rear ends carry sleeves 59 and wing nuts 63 by which said sleeve may be engaged with the rear forks. It will be noted that the bolts 5! thus span the cover plates and that the forks 56 are so angled that the bolts will be caused to bear tightly against the cover plates forcing them tight over the openings 53 when the wing nuts 61! are turned up.

The rise:- plates 5! are secured at their ends by angles 6! to forward edges of the side sections 2-45 and these plates 55 terminate at the meeting lines between adjacent side sections as best seen in Fig. 5. The tread plates 56 then turn upwardly at rear ends 50 to meet lower edges of the riser plates and angles 82 are provided for making connections between the various plates. The angles 62 may be connected by bolts or pins {53 and obviously the end connections between the plates 5ii-5l and the angles 528l may be made detachable so that the transverse portions of the inner form may be removed and others of different length substituted to thus vary the width However, when such width adl'ustment is not desired it is evidently simplest to weld the plates 5i 5! to the sides of the form.

or course where width adjustments are contemplated the outer forms 28 through 23 may also be "removed and'replaced with others of different lengths.

The uppermost inner cover plate 5d may be Welded at its edges 65 over the opening 53 since the mold may be filled without removing this plate. As shown in Fig. 5 the adjacent inner tread and riser plates 50 and 5| are each formed in one piece for convenience in assembly.

The uppermost tread T may be extended, along with the sides S, in a rearward direction to form a platform P and for this purpose I provide the platform or extension mold designated generally at A". The outer form B of this mold is made up of sides having the sections Iii, H l2 and 13 equal in number and vertical width to the corresponding outer side sections IE! to H3 but of equal length so that, when connected together by the angles 56, and bolts or pins 61 and wedges 68, they may be butted flush against rear outer edges of the main mold. End angles 59 on the meeting edges of all of the outer side sections may then be connected by bolts pivoted at H to the side section HJ!3 and fitting notches 12 in the outwardly turned webs of those angles 69.

By turning up the wing nuts I3 on these bolts it is apparent that these outer sides of the extension mold may be readily and rigidly secured to the main mold.

An additional outer transverse form member or plate I4 is then secured between these assembled outer sides of the extension mold and is removably secured flush with the uppermost tread plate 58 by angles I5 on the meeting edges secured together by the bolts IS. The uppermost extension side section I3 has an outwardly bulged portion I8 to extend the nosing N alongside .the

platform P.

The inner extension form, designated generally at C, comprises inner sides made up of sections 42 43 49 and 95 corresponding in width and arrangement to the sections 42-45 and secured together in edge to edge relation by angles I9 and bolts or pins 89 and wedges 8!. There is also provided an inner transverse member 82 for molding the inner or under platform surface and having an opening 83 which may be closed by a cover plate 84, either permanently or removably mounted.

On this inner form the respective horizontally aligned side sections 42-45 and 42 -45 fall short of meeting at their adjacent ends and are turned or extended inwardly in spaced relation for some distance as designated at 85 (Fig. while adjacent ends of the uppermost transverse members 59 and 82 are likewise spaced apart and.

turned downwardly as designated at 86. There is thus formed across the underside and vertically along each inner side a molding cavity such that there will be formed an arch or brace rib as indicated at 8?. The edges of the extended mold portions 85 and 86 are flanged at 83 and turned in opposite directions and the open edges of the mold cavity at this point may be closed by side closure strips 89, and a bottom closure strip 99, which have their margins 9| folded back on themselves for strengthening purposes and which are rested flat against the flanged margins 88. To secure the closure strips 89-99 inplace, I may employ clamps 92 having hooks 93 to fit over the edges of the strips and flanges 8B and connected by clamp bolts 94 having wing nuts 95. The hooks 93, due to their V-shape, will clamp the strips 89 and 99 tightly in place as will be readily apparent.

At their rear ends the inner extension form side sections I2= -45 and the transverse inner form member I2 are also turned respectively inwardly and downwardly as represented at 96-91 short of the rear end of the outer extension form B and these turned portions are flanged as shown at 98. A rear end closure member 99 of substantially U-shaped form having sides I 90 and top I III may be secured to the rear ends of the outer extension side sections Hi -H and I4 by pivoted swing bolts I92 and wing nuts I93, the rear ends of said form sections having angles I94 and both these angles and the sides of the member 99 having notches I 85 to receive said bolts; The member 99, when thus mounted, extends inwardly and downwardly in spaced relation to the correspond ing turned inner form portions 9891 and has marginal flanges I96 in alignment with the flanges 98. Closure strips I91 and I98 for sides and bottom are laid against these flanges and secured thereto by clamps 92, like those previously described, thus enclosing a'casting cavity which will form a rear end arch or rib I99 across the inner and undersides of the cast structure at its extreme rear end. The upper edge of closure member 99 has tongues 99 to releasably engage clips 99 on 5 the rear angle on member I4 to hold the member in place.

Attention is directed to the shape (in cross section) of the end closure member 99. The margins of this member on both sides I99 and top I9I are ofiset rearwardly as shown at I II] to dispose a narrow marginal portion III rearwardly of the plane of the sides and top and thereby cause the formation, at the rear of the platform, of a narrow rim I I2. When the cast stepsand platform are to be positioned against the building this narrow rim I I2 facilitates the fitting. For example, in a rough stone or block foundation-only a narrow strip (of inverted U-shape) need be chipped off smooth to fit the rim.

It may be desirable to cut off the corners of the lower edges of the side portions of the arches or ribs 81 and Hand as shown at H3 and for this purpose I provide at each corner the narrow angularly bent plate or strip I I4 (Figs. 7 and 8) which may be angularly supported in proper position in the form by a bracket plate I I5 removably mounted and supported by bolts I I6. This will prevent these corners from being broken Oh.

The inner mold when assembled in disposed within the outer mold and is supported in spaced relation thereto by cross bars I I I bolted at their ends at I I8 to the base angles I5-I6 and at inwardly spaced points bolted at I I9 to the base angles 46-19 of the inner forms. These cross bars are each made up of two parallel spaced angles I29, through horizontal webs of which are passed the bolts H8 and H9, and which are trussed and braced by bars IZI and truss rods I22 welded in place. Between the outer form and the cross bars I! l shims I23 are placed and apertured to pass the bolts I I8 while similar shims I24 are placed between the bars and inner forms likewise apertured to pass the bolts H9. Theoutermost shims I23 overlie the casting" cavities between the forms and in alignment therewith tapped blocks or nuts I25 are welded between the angles I20 to receive and pass the threaded screws or studs I26 having handles or cranks I21 at their ends;

In use the mold is inverted for casting as shown in Fig. 5 and in that position it is supported and rested in a stand I28 having'legs or posts I29 of varying length to support cross members I29 fitting beneath the steps as clearly shown. To prevent the platform section of the mold from sagging, from the weight of the concrete placed therein, a cross strap I39 is secured at its ends to a cross beam I3I placed beneath the mold and is trussed beneath a center'angle I32. Bolts I33 are connected to each end of the cross strap I39 and extended upwardly alongside the mold where they are engaged in clips I94 on the side sections I39 and drawn tight by wing nuts I35 to thereby upwardly brace the center and bottom of the mold.

When arranged in this inverted position the mold is filled by pouring in the concrete through the open edges of the sides and spaces forming the arches 81 and I99, starting of course at the lower parts of the mold and working upwardly. Prior to filling, reinforcing wires or rods designated generally at 'ISG'are placed in the mold in order to brace and reinforce the concrete. As the filling proceeds the cover plates and strips 54, 89, 99, I91, and I98 (all of which are at first removed) are replaced and clamped after the concrete is poured through the open ngs which they close, after which, when the mold is filled clear to the top, the upper I edges are struck off by a trowel. The mold is then left in position until the concrete has set; either naturally or by steam curing, after which the inner forms CC' are removed bodily. To accomplish this the outer bolts '8 are first removed and the cranks I21 turned to urge the screws I26 downwardly against the shims I23 resting on the outer form and casting. The upward pressure thus exerted lifts the inner form bodily until it is free of the casting and it may then be raised by a crane or other lifting device (not shown) until it is entirely clear. Attention is directed to the fact that all vertical portions of the inner form angle or converge toward the intended lower side of the cast structure in such manner as to facilitate this removal of the form. Obviously too the thickness of the cast structure may be varied by adjustment of the screws I26 or by removing one or the other of the shim plates -I23--I24 at each end of the cross bars I".

To remove the outer forms the casting, enclosed in these forms, is reverted bodily to normal or upright position and in so doing the casting may be braced in place by cross pieces (not shown) secured between margins of the outer form or the casting may be retained by the nosing N in the form. When thus positioned the back 99 is first swung clear and removed, and then the outer tread and riser forms 23, 22, 2| and 20 are swung clear one at a time as shown in Fig. 1, this swinging movement clearing the nosings N without difiiculty, and upper form 23 carrying member I4 clear. The outer sides may be finally pulled clear leaving the cast structure free for further curing.

These operations of pouring and removing the castings may be carried out very rapidly and the form, due to the conveniently operated fastenings employed, may be quickly assembled and disassembled as required.

To vary the number of steps cast the lower side sections including the inner and outer form members may be bodily removed one at a time as should be clearly apparent. For example to cast only three steps in a unit the lower form members II), III, 20, 42, 42 50 and 5| would be removed and the cross bars II'I located then on the next upper side members. All of the angles I5, 66, 46 and I9 are appropriately apertured for these adjustments. In practice it is found that (for instance) a seven step stair may be readily assembled by casting separate four step and three step units and mounting one atop the other, cast slabs or stones being used to fill in the platform sides, for the additional length thus made necessary. The lowermost form 20 is always used as the lower step form, replacing forms 2I, 22 or 23 as required.

Also it is possible to entirely remove the extension forms B and C where no platform is desired. In this case then the rear end closure 99 is removed and placed at the rear of the uppermost tread T where it may be readily mounted in place of the removed forms as represented in dotted lines in Fig. 5. In this case the narrow edge 2 is again formed at the rear of the stair structure. Likewise such removability of the extension forms B and 0' permits their convenient replacement with others of different length where a platform of larger size may be required.

For convenience in inverting and reverting the mold I provide hanger plates I31 which are secured by'bolts or studs I38 to outer sides of the form B as best seen in Fig. 1. These plates have five irregularly spaced openings I39 the positions of which are calculated to be on the transverse centers of gravity or balance axes of the mold when the same is assembled in its five possible arrangements. Hanger bails I40, supported by an overhead hoist or crane (not shown), carry pins I M which may be engaged in these openings I39 to raise and support the mold while it is turned. Thus in the position shown the pins MI serve as pivot axes about which the mold is balanced when it is set up to cast four steps and a platform. By shifting the pins the mold may be balanced when set up to cast three steps, two steps, or one step, all with, or without, platforms.

It has been found that vibration of the mold while the cementitious material is being poured, and while it is setting, is very important in order to achieve best results. Vibrators of the electromagnetic type, such as known by the trade name of syntron may be employed, or mechanical vibration may be used as thought best. As representative of one method which experience has proved to be effective I show herein an electromagnetic vibrator I42 secured by its base or clamp I43 to the hanger plate I31 at each side of the outer form. Also I may mount the vibrator on the inner form as described in my copending application Serial No. 388,772, hereinbefore referred to.

The outer tread forming plates 25 are provided with outwardly pressed bosses or shallow recesses I44 which will form non-skid protuberances I45 on the steps as shown. These nonskids are substantially rectangular and truncated in form with upwardly sloping sides and ends as clearly shown leaving their tops flat and in removing the forms the swinging movement of the outer tread forming plates 25 will also clear these protuberances. The shape of the non-skids is important as the sharp edges are found to remain even when the tops are worn down by use.

Under some circumstances, it may be desirable to cut off the lower edge of the casting less than the amount which would result from removing the parts casting the lowermost step. In such a case a out 01f strip or bafile I46 may be lowered into the casting cavity between the inner and outer forms as seen in Fig. 4 and supported at any desired level therein by threaded studs I41 secured to cross pieces I48 bolted to the forms. This baffle will thereby prevent the material from rising above and will reduce the height of the stair wherever required. Obviously the bafiies may be of any shape and length required and it is possible furthermore in this manner to cut off one or more. complete steps without dismantling the mold. A similar baflie (not shown) may be arranged in the rear of the mold if it is desired to shorten the cast structure to fit any particular installation.

To improve the appearance of the sides 8 of the cast stair, I arrange bars I49 in spaced relation along the inner side of each side section II]I3 and I Il --43 so as to form intaglio grooves I50 giving a panelled effect to the sides.

To aid in properly aligning and fastening the form sections 20 through 23 and I4 pilot or dowel pins 48 are welded to the sides of the mold to enter openings in these sections as clearly shown. Similarly other dowel pins 49 are placed about the mold wherever their use will be of help.

The forward portion of the'mold, particularly if it be a wide one, may be prevented from spreading by use, of a clamp |l similar to those heretofore referred to at 92 as seen in Fig. 5'.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appendedkclaims; Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. A mold for precasting a series of integral concrete steps, comprising inner and outer side forms for molding sides of the steps, the said side forms being made of sections each equal in height to one step, means traversing each section of the side forms for casting treads and risers of the steps, and means for assembling the side form sections and associated tread and riser molding means in preselected member and arrangement for casting a corresponding number of steps.

2. A mold for precasting a concrete stair structure having a plurality of steps and side walls therefor, comprising inner and outer forms each having side members for casting the sides and tread and riser portions for casting the steps between said sides, and said inner and outer forms being formed of sections removably connected along horizontal meeting edges.

3. A mold for casting a concrete stair structure having steps and side walls, the said mold comprising main inner and outer forms having side members forming said side walls and center members forming the steps, and an extension mold having inner and outer extension forms for extending the length of the side walls and uppermost step, the said main and extension forms being detachably connected at their meeting ends.

4. A mold for precasting concrete stair structures, including a plurality of steps having tread and riser portions, the said mold comprising inner and outer mold forms spaced apart to define molding cavities therebetween, the said outer form including a riser and tread molding member for each step and each member comprising two plates joined at right angles at meeting edges and having means at said joined edges for casting a nosing on outer edges of the said tread portions, and the said riser and tread molding members being swingably mounted for removal from the mold and for clearing the said nosings.

5. A mold for casting concrete stair structures having steps and sides, comprising spaced inner and outer members for forming the sides, inner and outer form members removably supported between the side forming members and shaped to form step treads and risers, the said inner form member comprising a frame having tread and riser forming portions, the said tread forming portions of the inner form having openings, plate members for closing the said openings, and means for removably clamping the plates over the openings.

6. A mold for precasting a series of steps having sides and a platform extension in one monolithic unit, comprising inner and outer forms adapted to be inverted and reverted in the molding process, said forms being separable along horizontal and vertical lines to cast any selected number of steps with or without the platform extension, hangers adapted for pivotal engagement with the forms to support the same for inverting and reverting movements, and pivot means on the mold for engaging the hangers, said pivot means being adjustable on the mold to various positions adapted to substantially balance the mold on the hangers when the mold is set up for casting various numbers of steps both with and without the platform extension.

7. A mold for precasting a plurality of stair steps in a monolithic unit, including an outer form having side members and tread and riser forming portions for each step, bolts pivotally mounted on the side members, the ends of the tread-and riser forming portions having notches for receiving the bolts, and wing nuts on the bolts adapted to engage the ends of the tread and riser forming portions to draw same tight against the side members.

8. In a mold for precasting a plurality of steps in a monolithic unit, a form having side members and transversely extending tread and riser forming members for each step, the tread and riser forming members for each step being of right angled shape, and the edge of one riser member having a clip and the'edge of the adjacent tread member having a strip hooked to engage said clip and adapted for releasable and swinging connection therewith.

9. A sectional mold for casting a predetermined number of stair steps and sides therefore in a monolithic structure, comprising inner and outer side forming sections and inner and outer tread and riser forming sections for each step, said side forming sections being capable of being set up in superimposed relation and removably fastened together and said tread and riser forming sections similarly arranged to define casting cavities for forming a predetermined number of steps and the sides therefor, and a platform extension mold, said extension mold including inner and outer side forming sections each corresponding in height to the height of corresponding side forming sections of the step mold, and means for detachably connecting said sections of the extension mold to each other and to the corresponding sections of the step mold.

10. In a mold of the character described for casting a series of stair steps and sides therefor in a monolithic structure, main inner and outer side forms and connecting center forms for easting the steps and sides, an extension mold for extending the sides and uppermost step, said extension mold having inner and outer side forms and a center form, means for detachably connecting the extension mold at one end to the ends of the main side forms and uppermost center form of the main mold, and a closure member for closing the other end of the said extension mold, said closure member being removable from the extension mold for engagement with the end of the main mold when said extension mold is removed.

11. In a mold for casting a series of stair steps and sides therefor, inner and outer forms arranged in spaced relation to define casting cavities therebetween, cross members connected to said forms, screw members engaging said cross members for movement into and out of said casting cavities, and baille members carried by said screw members and adjustable thereby to close oif parts of said casting cavities.

12. A mold for casting a series of stair steps with sides in a monolithic structure, comprising inner and outer side forms for molding the sides of the steps, said side forms being of sectional construction comprising sections each approximately equalling the height of one step, means removably mounted crosswise of corresponding opposite side form sections for molding the tread and riser of each step, and said side form sections and tread and riser forming means being arranged tobe set up in predetermined number for casting a corresponding number of steps.

13. A mold for casting a series of stair steps with sides in a monolithic structure, comprising inner and;outer side forms for molding the sides of the steps, said side forms being of sectional construction comprising sections each approximately equalling the height of one step, means removably mounted across one end and a part of the upper edge of each opposite pair of side form sections for molding the risers and treadsof each step,, andmeans for assembling the side form sections and associated riser and tread forming means-inpreselected number for casting a correspondingnumber of steps.

1.4, A mold for casting a concrete stair structure havingsteps and side walls, the said mold comprising main inner and outer forms having side members forming said side walls and center members forming the steps, and an extension mold having inner and outer extension forms for extending the length of the side walls and uppermost step, the said extension forms being arranged in end to end relation with the corresponding parts of the main forms, and means for detachably securing the main and extension forms in such relation.

15. A mold for precasting a series of steps having sides and a platform extension in one monolithic unit, comprising inner and outer forms adapted to be inverted and reverted in the molding process,- said forms being separable along horizontal and vertical lines to cast any selected number of steps with or without the platform extension, hangers adapted for pivotal engagement with the forms to support the same for inverting and reverting movements, hanger plates secured to the mold, and pivot means on said hanger plates for pivotally engaging the said hangers, the said pivot means being adjustable on the hanger plates to variously spaced positions adapted to substantially balance the mold on the hangers when the mold is set up for casting various numbers of steps with or without platform extension.

FRANK KOGL. 

